Four sum solution in java

Main.java

import java.util.*;

class Pair {
    int first;
    int second;

    public Pair(int first, int second) {
        this.first = first;
        this.second = second;
    }
}

class twoPair {
    // it's four pointer
    int first;
    int second;
    int three;
    int four;

    public twoPair(int first, int second, int three, int four) {
        this.first = first;
        this.second = second;
        this.three = three;
        this.four = four;
    }
}

class customComparatorTwoPair implements Comparator<twoPair> {
    public int compare(twoPair p1, twoPair p2) {
        if(p1.first == p2.first) {
            if(p1.second == p2.second) {
                if(p1.three == p2.three) {
                    return p1.four - p2.four;
                }
                return p1.three - p2.three;
            }
            return p1.second - p2.second;
        }
        return p1.first - p2.first;
    }
}

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int K = sc.nextInt();

        int[] arr = new int[N];

        for(int i=0; i<N; i++) {
            arr[i] = sc.nextInt();
        }
        Arrays.sort(arr);
        Map<Integer, ArrayList<Pair>> firstMap = new HashMap<>();

        for(int i=0; i<N; i++) {
            for(int j=i+1; j<N; j++) {
                addToPairList(arr[i]+arr[j], new Pair(i, j), firstMap);
            }
        } 
        findFourPairs(firstMap, K, N, arr);

    }

    public static void findFourPairs(Map<Integer, ArrayList<Pair>> firstMap, int K, int N, int[] arr) {
        Map<twoPair, Integer> secMap = new TreeMap<>(new customComparatorTwoPair());

        for(int i=0; i<N; i++) {
            for(int j=i+1; j<N; j++) {
                int curSum = arr[i] + arr[j];
                int rem = K - curSum;
                if(firstMap.containsKey(rem)){
                    ArrayList<Pair> temp = firstMap.get(rem);
                    for(Pair p : temp) {
                        if(i != p.first && j != p.first && i != p.second && j != p.second && j<=p.first)
                        secMap.put(new twoPair(arr[i], arr[j], arr[p.first], arr[p.second]) ,1);
                    }
                }
            }
        }

        //System.out.println(secMap);
        for(twoPair tp : secMap.keySet()) {
            System.out.println(tp.first+ " "+tp.second+" "+tp.three+" "+tp.four);
        }
    }

    public static void addToPairList(Integer key, Pair addThisPair, Map<Integer, ArrayList<Pair>> mapWithArrList) {
        ArrayList<Pair> temp = mapWithArrList.get(key);

        if(temp == null){
            temp = new ArrayList<Pair>();
            temp.add(addThisPair);
            mapWithArrList.put(key, temp);
        } else {
            if(!temp.contains(addThisPair)) {
                temp.add(addThisPair);
            }
        }
    }
}